Used Motorhomes For Sale By Owner What Year Were Slide Outs Introduced On Motorhomes?

What year were slide outs introduced on Motorhomes? - used motorhomes for sale by owner

We have used a study on the purchase of a Class C, in the near future, I wonder what the film first year modules have been introduced in Class C Motorhomes There is also a website dedicated to the older units in the reliability and common Problems?